Assisted cardiovascular circulation

ABSTRACT

Apparatus arranged to aid a patient&#39;&#39;s cardiovascular circulation by moving the patient synchronously and in proper phase with the pumping action of his heart to reduce the pumping load on his heart. An improved cardiovascular circulation aid is disclosed utilizing apparatus for providing an accurate indication of the occurrence of onset of systole and where body movement is precisely synchronized thereto. Apparatus for phasing the onset of systole with the beginning of movement of the patient includes ultrasonic ranging and doppler devices, and/or an impedance plethysmograph.

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Ullll'C ueauia I ("Cut Goldberg 51 July 4, 1972 [541 ASSISTED CARDIOVASCULAR 3,498,290 3/1970 Shaw et al. ..12s/2.os F CIRCULATION 3,545,429 12/1970 Pelta et al ..l28/2.l Z

[72] Inventor: Herbert E. Goldberg, Concord, Mass. p i EmmiM, Lawmnce w Tripp [73] Assignee: American Optical Corporation .'1 .w i "l:. i filkx lifilyiul fi 3 9,!!-

s hbfid MwL Bird andBemard L. Sweeney [22] Filed: Oct. 2, 1970 57 ABSTRACT PP 77,662 Apparatus arranged to aid a patients cardiovascular circulation by moving the patient synchronously and in proper phase with the pumping action of his heart to reduce the pumping IIL "HS/33x0: load on his hem. An improved cardiovascuar circulation aid 58] dd sunk 128/2 24 2 33 5042 2 05 F is disclosed utilizing apparatus for providing an accurate indication of the occurrence of onset of systole and where body movement is precisely synchronized thereto. Apparatus for "an". phasing the onset of systole with the beginning of movement [56] of the patient includes ultrasonic ranging and doppler devices,

UNITED STATES PATENTS and/or an impedam plflhysmozraph- 3,532,089 10/1970 Amtzenius ..l28/33 7 Claims, 2 Drawing Figures I ultrosome transducer excitation and return slqnol processor repucl movement slow return PATENTEUJUL 4 m2 SHEET 1 0F 2 mm 4 E29? 2:26 332. 3 2 239 2 259 2:26 Saar:

INVENTOR. HERBERT E. GOLDBERG TTORNEYV P'A'TENTEnJuL 4 m2 SHEET20F 2 INVENTOR. HERBERT E. GOLDBERG 1 ASSISTED CARDIOYASCULAR CIRCULATION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the varying of work-load on a human heart, and more particularly relates to decreasing heart pumping load of a patient with a weak heart. Apparatus is provided for aiding a heart-patient's cardiovascular circulation by moving his body in a certain direction and synchronously with beating action of his heart, whereby the movement and the heartbeat have such a precise phase relationship as to cause the work-load on his heart to be substantially decreased.

2. Description of Prior Art US. Pat. No 3,532,089 to Arntzenius, issued 6 Oct, 1970, entitled Method and Device for Assisting Cardiovascular Circulation is the most pertinent prior art. The substance thereof is included herein by reference. This patent discloses an electro-mechanical system for aiding cardiovascular circulation by moving the body synchronously with pumping action of the heart. The system discloses particular apparatus including a table for supporting the human body in a supine position, a heartbeat sensing device such as an ECG, and a power device (preferably hydraulic) for moving the table synchronously with pumping action of the heart.

The heartbeat sensing device disclosed in the patent is selected from a group of four devices. They are an ECG, a pressure transducer of the implanted variety, an acceleration transducer, and a ballisto-cardiogram. No other devices are disclosed.

All of these devices have certain disadvantages. For example, the ECG represents an electrical wave-complex generated during beating action of the heart and accurate repetitive detection of the P-Q-R-S-T complex is sometimes difficult. In a given patient, the R-wave (which is usually the largest wave of the complex), does not always occur at a fixed time displacement from the onset of systole and is thus not completely dependable as a timing signal. And, in the case of aiding successive patients, because of differences from patient to patient in their respective myocardium conduction and contractility characteristics, the onset of systole is even less precisely determined with ECG apparatus) for each patient.

An implanted pressure transducer, although accurate in its determination of systolic pressure, has the disadvantage that implantation carries a risk of infection and is too delicate for routine clinical use. It is desirable to use a non-invasive sensing device. The acceleration transducer and ballisto-cardiogram, although non-invasive, sufier from other disadvantages. The indication of the occurrence of systolic pressure is not precise enough.

The cardiovascular circulatory aid, as disclosed in the system of the Amtzenius patent, is effective only if properly timed with the pumping action of the heart. The patent does not disclose reliable, non-invasive apparatus which has as much precision as desired. At the onset of systole, when the ventricular pressure is at a peak, blood in the ventricle is about to be forced into the aorta. If at this point in time, a sudden movement is applied to the heart (the body) in a direction that is generally axial with respect to that portion of the aorta adjacent the aortic valve and is in a direction towards the apex of the ventricle (away from the aortic valve), the pumping load on the ventricle imposed by the aortic valve and the aorta is substantially reduced.

The more accurate the timed relationship between the buildup of ventricular pressure and the sudden movement, the more effective the assistance to the heart. If, for example, the movement and the onset of systole are substantially out of phase, an increase in the pumping load occurs. This could be dangerous to heart-patient whose heart is weak. He needs assistance and not an extra work-load. (Extra load can be desirable, as for example in the case of healthy people where load is purposely placed on the heart to strengthen heart muscle.)

The present invention is non-invasive and provides more precise indications of systolic pressure than previously available. 'Ihe heartbeat sensing device of the present invention is more precise than any previously known external sensing devices and is as precise as the implanted pressure transducer without its disadvantages.

The present invention employs transducers external to the body. They provide precise signals for timing movement of the pau'ent and either occurrence of peak pressure of the left ventricle, onrush of blood flow in the aorta or pulsation of blood flow through the thoracic cavity. The occurrence of any one of these is an accurate indication of the onset of systole and is an indication of when movement shouldbe applied to the heart.

SUMMARY OF THE INVENTION The invention relates to a system for applying motion to the heart of a patient in an accurate phase relationship to onset of systole. The invention uses transducers that precisely determine onset of systole. The present invention, in one embodiment, utilizes an impedance plethysmograph to sense change in impedance of the thoracic cavity due to blood flow. In another embodiment, the present invention uses ultrasonic devices of the ranging and doppler variety in ultrasonic communication with the heart and aorta. These ultrasonic transducers precisely determine onset of aortic bloodflow or movement of the myocardium, indicating onset of systole.

An advantage of the present invention is that is provides a reliable, easily useable, and accurate means of timing or synchronizing the movement of a patient with his heartbeat to assist cardiovascular circulation. Timing is based on actual left ventricular pressure and not upon some representative phenomenon such as an ECG. Also the present invention does not require implantation.

It is an object of the present invention to provide an improved cardiovascular circulation assist.

It is a further object of the present invention to provide a reliable, and easily connectable device for obtaining precise timing information for synchronization of ventricular pressure with movement of the patient's heart.

Other objects and advantages of the present invention will become apparent to one having reasonable skill in the art after referring to the detailed description of the appended drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic view of apparatus according to the present invention;

FIG. 2 is a schematic diagram of the left ventricle and aorta of a human heart, in ultrasonic communication with an illustrative embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, patient 12 is supported on table 10 within bodyoutline conforming material 13, and is held down by straps 16. The patient's heart 14 is caused to reciprocate in directions L in response to application of power to two stage electrohydraulic servo valve 32, which in turn controls the operation of a piston cylinder hydraulic servo motor 34 which drives table 10. Hydraulic power system 29 receives its input signal from hydraulic control circuit 28 which in turn receives its input signals from feedback potentiometer 33 and from electronic circuitry. The circuitry comprises delay circuit 24, pulse forming circuit 26, trigger circuit 20 and frequency detector 22. Heartbeat sensing device 18 provides an electrical input to this electronic circuitry. Device 18 is a transducer which receives its pressure input signal from pumping action of the patient's heart. Detailed description of the operation of this circuitry is found in the Arntzenius Patent mentioned above and incorporated herein by reference.

FIG. 2 is a cross section of a human heart 114 showing the left ventricle and the aorta and the aortic valve. Rapid movement and slow return are in the directions depicted. The apparatus is shown in ultrasonic communication with the aorta and with left ventricle l 14. Transducer elements 128 and 122 in the preferred embodiment, are equivalent to transducer elements 28 and 22 of US. Pat. No. 3,498,290 to Shaw et al., entitled Pulsed Doppler Volumetric Blood Flow Meter," the subject matter of which is included herein by reference. Transducer element 122 locates and measures diameter of the aorta and transducer element 128 determines velocity of blood in the vessel by doppler frequency shift techniques. Aorta diameter and velocity of blood therethrough are used to provide a precise indication of blood flow at onset of systole. This determination is accomplished by ultrasonic transducer excitation and return signal processor 121 (a detailed description of a particular embodiment is included in the Shaw et al. patent referred to above). The output from transducer elements 128 and 122 are combined to provide information to frequency detector 22, and trigger circuit 20 so that they, in combination with pulse forming circuit 26 and delay circuit 24, provide a signal to the power system to appropriately move table and the patient thereon at a precise time with respect to the onrush of blood flow in the aorta.

Alternatively, or additionally, another transducer element can be used. Transducer element 124 is in ultrasonic communication (as shown by dashed lines 126) with heart 114. Reflected ultrasonic energy 125 which is detected by transducer element 124 and processed in processor 121, is an indication of movement of the heart wall (or myocardium) in response to blood pressure therein. This information can be used instead of, or in addition to, the information obtained from the aorta, as another input to the remaining electronic processing circuitry 121 to obtain a precise timing signal. When element 124 is used to detect systole, elements 122 and 128 can be used to provide a signal to a monitoring device used to monitor the overall operation of the system. Such a device can be an oscilloscope.

Transducer elements 128 and 122 comprise an ultrasonic doppler type flow measurement device, and transducer 124 comprises an ultrasonic ranging device. When both types of devices are used simultaneously, very accurate timing information is obtained, although as mentioned either type may be used alone.

Other transducers may be employed to obtain a precise timing signal. For example, an impedance plethysmograph, of the type disclosed in US. Pat. No. 3,340,867, to Kubicek et al., entitled Impedance Plethysmorgraph," can be used to determine a precise timing signal. The Kubicelt et al. patent is incorporated herein by reference. An impedance plethysmograph is a device adapted to be positioned external the chest in the vicinity of the thorax and is arranged to measure changes in the thoracic impedance due to cardiac output, or blood flow in the thorax.

The impedance plethysmograph can be used to provide a signal to a monitoring device used to monitor the overall operation of the system In this case, the timing of the system can be adjusted manually until optimum operation is observed on the monitoring device.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, transducer elements 122 and 128 can be directed on heart wall 114 rather than on the aorta. This would allow a volumetric flow computation related to the heart and provide precise timing information. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. In apparatus arranged to aid cardiovascular circulation in a patient by moving the body of said patient synchronously with pumping action of the heart of said patient to reduce pumping load on said heart, the improvement com rising:

ultrasonic transducer means operatrvely connec ed to external surface areas of said body responsive to operation of said heart for providing accurate timing for movement of said body.

2. Apparatus as recited in claim 1 wherein said ultrasonic means is in ultrasonic communication with said heart and is responsive to movement of said heart caused by said pumping action.

3. Apparatus as recited in claim 1 wherein said transducer means includes ultrasonic doppler means responsive to blood flow in said heart caused by said pumping action.

4. Apparatus as recited in claim 1 and wherein said transducer means includes ultrasonic doppler means responsive to blood flow in the ascending aorta of said patient caused by said pumping action, for indicating successive occurrences of said pumping action and monitoring means responsive to the operation of said doppler means and to the movement of said patient for monitoring the operation of said apparatus.

5. Apparatus as recited in claim 1 and wherein said transducer means includes phase means for causing the beginning of movement of said body to be related by a predetermined phase to the onset of systole.

6. In apparatus arranged to aid cardiovascular circulation in a patient by moving the body of said patient synchronously with pumping action of the heart of said patient to reduce pumping load on said heart, the improvement comprising:

impedance means adapted to be connected external the thorax of said patient responsive to thoracic impedance changes caused by said pumping action for providing accurate timing for movement of said body.

7. Apparatus as recited in claim 6 and wherein said impedance means includes an impedance plethysmograph.

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1. In apparatus arranged to aid cardiovascular circulation in a patient by moving the body of said patient synchronously with pumping action of the heart of said patient to reduce pumping load on said heart, the improvement comprising: ultrasonic transducer means operatively connected to external surface areas of said body responsive to operation of said heart for providing accurate timing for movement of said body.
 2. Apparatus as recited in claim 1 wherein said ultrasonic means is in ultrasonic communication with said heart and is responsive to movement of said heart caused by said pumping action.
 3. Apparatus as recited in claim 1 wherein said transducer means includes ultrasonic doppler means responsive to blood flow in said heart caused by said pumping action.
 4. Apparatus as recited in claim 1 and wherein said transducer means includes ultrasonic doppler means responsive to blood flow in the ascending aorta of said patient caused by said pumping action, for indicating successive occurrences of said pumping action and monitoring means responsive to the operation of said doppler means and to the movement of said patient for monitoring the operation of said apparatus.
 5. Apparatus as recited in claim 1 and wherein said transducer means includes phase means for causing the beginning of movement of said body to be related by a predetermined phase to the onset of systole.
 6. In apparatus arranged to aid cardiovascular circulation in a patient by moving the body of said patient synchronously with pumping action of the heart of said patient to reduce pumping load on said heart, the improvement comprising: impedance means adapted to be connected external the thorax of said patient responsive to thoracic impedance changes caused by said pumping action for providing accurate timing for movement of said body.
 7. Apparatus as recited in claim 6 and wherein said impedance means includes an impedance plethysmograph. 